The present invention relates to new N-acetylneuraminic acid derivatives, in particular to those having immunological activity and a method of the preparation thereof.
It has been known that N-acetylneuraminic acid exists in animals and on the cell surface of some bacteria as sialocomplex (glycoproteins, glycolipids, oligosaccharides, polysaccharides). Recently, it has been recognized that this compound is important medically and pharmaceutically in conditioning the function of nerve system, differentiation of cells and immunity, treatment of inflammatory, cancer, virus infection and as a hormone receptor and the compound has drawn attention to as a specific active molecule localized on the cell surface.
However, the roles of this compound in the sialo-complex are still a matter of conjecture.
A number of organic chemists who engage in the investigation of natural substances studied this compound and they reported various kind of simple derivatives thereof [see, for example, J. Biol. Chem., 244, 1306 (1969); Z. Physiol. Chem., 352, 1715 (1971)]. However, no derivative having a conspicuous physiological activity has yet been known.
Owing to the recently developed multilateral treatments for diseases such as every kind of cancer inclusive of malignant tumour of the hematogenic organs and collagenosis diseases, an apothanasia effect is, in fact, attained. While, an immoderate use of adrenocortical hormones and immunosuppressors is almost inevitable and therefore, the problem of side-effects as well as the reduction or decrease in so-called capacity of immunity are matter of grave concern.
Therefore, there is a strong demand for more safer and more effective medicines which causes no entrainment of serious side-effects.